Usually three different agents in different concentrations and mixtures are used for this purpose: Phenol, Trichloro-acetic-acid or Alpha-hydroxy-acids.
Phenol-peeling:
Phenol has a deep penetration and is the most powerful agent. Therefore some disadvantages as depigmentation, pain and hypersensibility to sun-exposure are common. Lighter buffered brands are commonly used today.
Trichloro-acetic-acid (TCA):
TCA does only have a relatively superficial effect but with a pre-peeltreatment with Retin-A and hydrochinone, a sufficiently deep effect is achieved.
Alpha-hydroxy-acids (AHA):
The AHA-s are since ancient ages in use and have recently gained a renaissance. The active agent is a component in commercially available different brands, mostly handed out by cosmeticians, who also usually make superficial peelings, whereas physicians should make deeper peels. The AHA´s gives the skin a "polish" but never removes scars or even wrinkles.